Files

SKILL.mdagentsreferencesscripts

Install

Install the containing plugin

/plugin install shared-skills@llm-skills

Invoke this skill after installation

/shared-skills:xmllint

Download xmllint-skill.zip

This skill is bundled inside shared-skills. Install the plugin once, then Claude Code can use any of its included skills. Browse the full plugin repository at github.com/alisonaquinas/llm-shared-skills.

SKILL.md

name: xmllint description: > Parse, validate, format, and query XML documents using xmllint from libxml2. Use when the task involves checking XML well-formedness, validating against a DTD or XML Schema (XSD), validating against RelaxNG or Schematron, running XPath queries to extract values from XML, pretty-printing or reformatting XML, or recovering structure from malformed XML. Also use when processing untrusted XML and network access must be blocked to prevent XXE attacks.

xmllint

Parse, validate, format, and query XML documents. Part of the libxml2 toolset.

Prerequisite Check

Run this before proposing validation or XPath workflows:

command -v xmllint >/dev/null 2>&1 || xmllint --version

If xmllint is missing, surface that first and either run scripts/install.sh or scripts/install.ps1, or fall back to xq for query-oriented work and xml2 for shell-pipeline transformations.

Intent Router

Request	Reference	Load When
Install xmllint	`references/install-and-setup.md`	Setting up on a new system
Flags, options, one-liners	`references/cheatsheet.md`	Need quick command lookup
XPath queries, schema workflows	`references/advanced-usage.md`	Complex validation or extraction tasks
Errors, exit codes, common failures	`references/troubleshooting.md`	Something is failing or output is unexpected

Quick Start

Confirm the binary: xmllint --version
Start with a safe well-formedness check: xmllint --nonet --noout file.xml
Add schema or DTD validation only when the schema source is known
Use --xpath for targeted extraction instead of printing whole documents
If xmllint is unavailable, state the fallback boundary to xq or xml2

Quick Reference

# Check well-formedness (exit 0 = valid)
xmllint --noout file.xml

# Pretty-print / reformat
xmllint --format file.xml

# Custom indentation (tab)
XMLLINT_INDENT=$'\t' xmllint --format file.xml

# Validate against XML Schema
xmllint --noout --schema schema.xsd file.xml

# Validate against DTD embedded in document
xmllint --noout --valid file.xml

# XPath query
xmllint --xpath '//book/title/text()' file.xml

# Block network access (safe for untrusted XML)
xmllint --nonet --noout file.xml

# Attempt recovery from malformed XML
xmllint --recover file.xml

Core Workflow

Check availability: xmllint --version
Verify well-formedness: xmllint --noout file.xml
Validate against schema if available: xmllint --noout --schema schema.xsd file.xml
Query specific values: xmllint --xpath 'expression' file.xml
Format for readability: xmllint --format file.xml

Security: XXE Prevention

By default, xmllint fetches external DTDs and entities from the network. When processing untrusted XML, always add --nonet:

# Safe invocation for untrusted input
xmllint --nonet --noout file.xml
xmllint --nonet --schema schema.xsd file.xml

--nonet blocks all network access during parsing and validation.

Verification cue: a safe baseline run is xmllint --nonet --noout file.xml. If that fails because the binary is missing, stop at install guidance instead of presenting later validation commands as runnable.

Safety Notes

Area	Guardrail
Untrusted XML	Always use `--nonet` to prevent XXE (XML External Entity) attacks.
Validation output	Use `--noout` to suppress the parsed tree — show only errors.
Large files	Test with `--noout` first; full output of large files can be verbose.
Recovery mode	`--recover` may produce incomplete or structurally incorrect output. Validate the result.

Recovery note: when xmllint is unavailable, say whether the task is still answerable with xq or xml2. Neither fallback fully replaces schema validation.

Resource Index

scripts/install.sh — Install libxml2-utils on macOS or Linux
scripts/install.ps1 — Install on Windows via Chocolatey